168 lines
7.1 KiB
C
168 lines
7.1 KiB
C
/** library for enhanced USART communication (code)
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* @file usart_enhanced.c
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* @author King Kévin <kingkevin@cuvoodoo.info>
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* @copyright SPDX-License-Identifier: GPL-3.0-or-later
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* @date 2018-2021
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* @details the USART peripherals only support 8 or 9-bit word and even or odd parity (included in the data bits). The library adds support for 5 to 8-bit words, none/even/odd/mark/space parity (on top of the data bits)
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* @note since parity is handled in software, the parity error (PE) flag is unused and should be replaced by the value return by usart_enhanced_parity_error
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* @remark 9-bit raw communication is not supported since this is not common and can be done without this library
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*/
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/* standard libraries */
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#include <stdint.h> // standard integer types
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/* STM32 (including CM3) libraries */
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#include <libopencm3/stm32/usart.h> // USART utilities
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/* own libraries */
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#include "usart_enhanced.h" // utilities for USART enhancements
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/** number of available USART peripherals */
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#define USART_PERIPHERALS_NB 3
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/** configured enhanced USART word size */
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static uint8_t usart_enhanced_databits[USART_PERIPHERALS_NB];
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/** configured enhanced USART parity */
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static enum usart_enhanced_parity_t usart_enhanced_parity[USART_PERIPHERALS_NB];
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/** last enhanced USART parity error status */
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static bool usart_enhanced_parity_errors[USART_PERIPHERALS_NB];
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const bool usart_enhanced_even_parity_lut[256] = { true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, };
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/** get index of corresponding enhanced USART configurations
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* @param[in] usart USART peripheral base address
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* @return index used for the individual USART configurations
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* @note the returned value is valid only is less than USART_PERIPHERALS_NB
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*/
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static uint8_t usart_enhanced_id(uint32_t usart)
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{
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uint8_t to_return = USART_PERIPHERALS_NB;
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switch (usart) {
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case USART1:
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to_return = 0;
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break;
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case USART2:
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to_return = 1;
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break;
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case USART3:
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to_return = 2;
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break;
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default:
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to_return = USART_PERIPHERALS_NB;
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break;
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}
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return to_return;
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}
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bool usart_enhanced_config(uint32_t usart, uint8_t databits, enum usart_enhanced_parity_t parity)
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{
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/* sanity check */
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uint8_t id = usart_enhanced_id(usart);
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if (id >= USART_PERIPHERALS_NB) {
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return false;
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}
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if (databits < 5 || databits > 8) {
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return false;
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}
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if (parity > USART_ENHANCED_PARITY_SPACE) {
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return false;
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}
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// save configuration for later use
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usart_enhanced_databits[id] = databits;
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usart_enhanced_parity[id] = parity;
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// configure USART peripheral
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if (8 == databits && USART_ENHANCED_PARITY_NONE != parity) { // the parity bit is additional to the data bits
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usart_set_databits(usart, 9);
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} else {
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usart_set_databits(usart, 8);
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}
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usart_set_parity(usart, USART_PARITY_NONE); // set no parity since we will take care of it ourselves
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// we could also lower the number of stop bits when less than 8 bits are used, for higher throughput, but this is not a good idea since most UART transceiver parse 8 bits even is less is used
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return true;
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}
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void usart_enhanced_send(uint32_t usart, uint8_t data)
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{
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/* sanity check */
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uint8_t id = usart_enhanced_id(usart);
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if (id >= USART_PERIPHERALS_NB) {
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return;
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}
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data &= ~(0xff << usart_enhanced_databits[id]); // only keep the data bits
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uint16_t output = data; // put value in output buffer
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switch (usart_enhanced_parity[id]) {
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case USART_ENHANCED_PARITY_NONE: // a mark is also decoded as idle/stop
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case USART_ENHANCED_PARITY_MARK:
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output |= (1 << usart_enhanced_databits[id]); // add idle state
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break;
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case USART_ENHANCED_PARITY_EVEN:
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if (!usart_enhanced_even_parity_lut[data]) {
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output |= (1 << usart_enhanced_databits[id]);
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}
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// no need to clear a bit if the parity is even
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break;
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case USART_ENHANCED_PARITY_ODD:
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if (usart_enhanced_even_parity_lut[data]) {
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output |= (1 << usart_enhanced_databits[id]);
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}
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// no need to clear a bit if the parity is odd
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break;
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case USART_ENHANCED_PARITY_SPACE:
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// no need to clear the bit
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break;
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}
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output |= (0xffff << (usart_enhanced_databits[id] + 1)); // set additional bits to idle (high)
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usart_send(usart, output); // transmit character
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}
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uint8_t usart_enhanced_recv(uint32_t usart)
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{
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/* sanity check */
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uint8_t id = usart_enhanced_id(usart);
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if (id >= USART_PERIPHERALS_NB) {
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return 0xff;
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}
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uint16_t input = usart_recv(usart); // read received character (also clears the error flags)
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uint8_t data = input & ~(0xffff << usart_enhanced_databits[id]); // only keep the data bits
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// check the parity
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uint16_t parity = input & (1 << usart_enhanced_databits[id]); // only keep the parity bit
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usart_enhanced_parity_errors[id] = false;
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switch (usart_enhanced_parity[id]) {
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case USART_ENHANCED_PARITY_NONE:
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usart_enhanced_parity_errors[id] = false;
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break;
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case USART_ENHANCED_PARITY_EVEN:
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if (parity) {
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usart_enhanced_parity_errors[id] = !usart_enhanced_even_parity_lut[data];
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} else {
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usart_enhanced_parity_errors[id] = usart_enhanced_even_parity_lut[data];
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}
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break;
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case USART_ENHANCED_PARITY_ODD:
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if (parity) {
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usart_enhanced_parity_errors[id] = usart_enhanced_even_parity_lut[data];
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} else {
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usart_enhanced_parity_errors[id] = !usart_enhanced_even_parity_lut[data];
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}
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break;
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case USART_ENHANCED_PARITY_MARK:
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usart_enhanced_parity_errors[id] = !parity;
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break;
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case USART_ENHANCED_PARITY_SPACE:
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usart_enhanced_parity_errors[id] = parity;
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break;
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}
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return data;
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}
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bool usart_enhanced_parity_error(uint32_t usart)
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{
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/* sanity check */
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uint8_t id = usart_enhanced_id(usart);
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if (id >= USART_PERIPHERALS_NB) {
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return false;
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}
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return usart_enhanced_parity_errors[id];
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}
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